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Abstract:

A brake disk including carbon steel, stainless steel or a ceramic
composite material and coated with a coating material that is wear and
corrosion resistant and when applied properly allows for the coated
surface to have a variety of "textured" appearances. For example, the
coated surface can be made to look like woven carbon fiber. The
aesthetically pleasing, wear and corrosion resistant coating overlays
wear surfaces and portions of the brake disk that will be, in many cases,
visible when the brake disk is installed on the vehicle. The coating
includes a first layer of a metal, such as a pure titanium metal, and a
second layer that can include a Nitride, Boride, Carbide or Oxide of the
metal used in the first layer. The coating can be applied using a
physical vapor deposition source such as a cathodic arc source with a
controlled gas atmosphere.

Claims:

1. A method for manufacturing a coated brake disk having parallel
surfaces comprising: surface finishing at least a portion of the parallel
surfaces of a brake disk to impart a predetermined three dimensional
surface texture having peaks, valleys and angular surfaces between the
peaks and valleys; applying a first material to at least a portion of the
parallel surfaces of the brake disk through vapor deposition, wherein the
first material is deposited onto the brake disk by energizing a first
material source to cause charged particles of the first material source
to be dissociated from the first material source and deposited on the
parallel surfaces of the brake disk; and applying at least a compound to
the at least a portion of the parallel surfaces of the brake disk through
vapor deposition, wherein the second compound is deposited by energizing
a second material source to cause charged particles of the second
material source to be dissociated from the second material source,
introducing a reactive gas which reacts with the charged particles of the
second material forming the compound that is deposited on the parallel
surfaces of the brake disk; wherein the combination of the surface
finishing and the depositing causes the at least a portion of the
parallel surfaces of the brake disk to exhibit a selected three
dimensional surface texture.

2. The method of claim 1, wherein the first material is a metal with an
amorphous structure.

3. The method of claim 1, wherein the first material is a metal with a
crystalline structure.

4. The method of claim 1, wherein second material is a binary metal.

5. The method of claim 4, wherein the binary metal is selected from the
group consisting of a metal nitride, a metal oxide, a metal boride and a
metal carbide.

6. The method of claim 1, wherein the three dimensional surface texture
is selected from the group consisting of a woven structure and a textured
structure.

8. The method of claim 1, wherein the applying a first material
comprises: engaging the parallel surfaces of the brake disk with a
fixture of a deposition apparatus comprising at least two linear
deposition sources with each of the deposition sources lying parallel to
an axis and each of the deposition sources being a source of the first
material; and rotating the fixture in a planetary movement about the axis
and operating the deposition sources to deposit the first material to the
parallel surfaces of the brake disk.

9. The method of claim 1, wherein each of the linear deposition sources
is selected from the group consisting of a cathodic arc source, a
magnetron sputtering source and an evaporative source.

10. A coated brake disk comprising: a brake disk substrate having
parallel surfaces, at least a portion of the parallel surfaces applied
with a surface finish to impart a predetermined three dimensional texture
to the parallel surfaces of the disk brake, wherein the outermost layer
of the parallel surfaces of the disk brake maintains the predetermined
three dimensional appearance when coated with at least a first layer of a
first coating material and at least a second layer of a second coating
material by vapor deposition.

11. The coated brake disk of claim 10, wherein the second coating
material is selected from the group of coating materials consisting of
metal nitride, metal oxide, metal boride and metal carbide.

12. The coated brake disk of claim 11 wherein the metal nitride is a
nitride of an active metal selected from the group of active metals
consisting of titanium, chromium, zirconium, boron, hafnium and alloys
thereof.

13. The coated brake disk of claim 11 wherein the metal oxide is an oxide
of an active metal selected from the group of active metals consisting of
titanium, chromium, zirconium, boron, hafnium and alloys thereof.

14. The coated brake disk of claim 11 wherein the metal boride is a
boride of an active metal selected from the group of active metals
consisting of titanium, chromium, zirconium, boron, hafnium and alloys
thereof.

15. The coated brake disk of claim 16, wherein first coating layer
comprises a metal with either an amorphous structure and/or a crystalline
structure, said metal being selected from the group of metals consisting
of titanium, chromium, zirconium, boron, hafnium and alloys thereof.

16. A method for manufacturing a coated brake disk having parallel
surfaces comprising: surface finishing a portion of the parallel surfaces
of a brake disk to impart a predetermined three dimensional pattern to
the portion of the parallel surfaces of the disk brake, the three
dimensional pattern including peaks, valleys and angular surfaces between
the peaks and valleys; applying at least a first layer of coating to the
portion of the parallel surfaces of the brake disk with at least a first
coating material through vapor deposition; and applying at least a second
layer of coating to the portion of the parallel surfaces of the brake
disk with at least a second coating material through vapor deposition
wherein more of the second layer of coating is deposited on the peaks
than is deposited on the angular surfaces between the peaks and valleys;
wherein the outermost layer of the parallel surfaces of the brake disk
maintains the predetermined three dimensional appearance after depositing
the at least first and at least second layers.

17. A method for manufacturing a coated brake disk having parallel
surfaces comprising: surface finishing at least a portion of the parallel
surfaces of a brake disk to impart a predetermined three dimensional
surface texture having peaks, valleys and angular surfaces between the
peaks and valleys; applying a first material to at least a portion of the
parallel surfaces of the brake disk through vapor deposition; and
applying at least a second material to the at least a portion of the
parallel surfaces of the brake disk through vapor deposition, wherein
more of the second layer of coating is deposited on the peaks than is
deposited on the angular surfaces between the peaks and valleys; wherein
the combination of the surface finishing and the application of the first
and second materials causes the at least a portion of the parallel
surfaces of the brake disk to exhibit a predetermined three dimensional
surface texture.

19. The method of claim 1 wherein the first material source and the
second material source are the same material.

Description:

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation of U.S. patent application Ser.
No. 14/711,661, filed May 13, 2015, titled "Wear Resistant Coating For
Brake Disks With Unique Surface Appearance and Methods For Coating;"
which in turn is a continuation of U.S. patent application Ser. No.
13/336,986, filed Dec. 23, 2011, titled "Wear Resistant Coating For Brake
Disks With Unique Surface Appearance and Methods For Coating;" which in
turn is a divisional of U.S. patent application Ser. No. 12/034,590,
filed on Feb. 20, 2008 and issued as U.S. Pat. No. 8,084,089 on Dec. 27,
2011, which claims priority under 35 U.S.C. §119(e) to U.S.
Provisional Patent Application Ser. No. 60/890,790, filed Feb. 20, 2007.
The disclosure of each application listed in this paragraph is hereby
incorporated by reference in its entirety.

FIELD OF THE INVENTION

[0002] The present invention pertains generally to coated brake disks,
drums or any mechanical device that uses friction to transfer kinetic
energy, and methods for coating brake disks and drums. More particularly,
the present invention pertains to brake disks and drums which have
various surface finishes that when coated with a wear and corrosion
resistant coating exhibit a three dimensional appearance or surface
texture. The present invention is particularly, but not exclusively,
useful as a brake disk for use on motorcycles, bicycles, automobiles and
any other motor vehicle.

BACKGROUND

[0003] There are a number of reasons why it is important for a brake disk
(also sometimes referred to as a brake rotor) to be wear and corrosion
resistant while at the same time looking aesthetically pleasing. First,
the ability of the brake disk to resist wear leads to a longer service
life. A longer service life translates into reduced maintenance and the
associated maintenance costs. Additionally, the ability of the brake disk
to resist corrosion adds to the life and the overall appearance of the
brake disk. Another consideration for brake disks used on motorcycles (or
wherever the brake disk is exposed to general view), is the appearance of
the brake disk.

[0004] During braking, hydraulic or mechanical energy is used to press the
vehicle's brake pads against the rotating brake disk. The friction
resulting from the moving contact between brake pad and brake disk slows
the rotation of the brake disc and decreases the speed of the vehicle.
This frictional contact generates heat and causes the contact surfaces on
the brake pad and brake disk to wear unevenly. Excessive wear can cause
the brake disk to become thin and weak. In some cases, the thinning of
the brake disk becomes so severe that the brake disk is no longer able to
support the stresses and heat generated during braking. The result is
typically a warped brake disk that can cause undesirable brake
chattering.

[0005] A final factor that must be considered when designing brake rotors
is aesthetics. Modern motorcycles have rather large diameter brake disks
that are plainly visible, especially the front disk. Because of this
visibility, the color and surface appearance of a brake disk can add to
or detract from the overall look of the motorcycle. These considerations
can affect a purchaser's decision when buying a new motorcycle and when
retrofitting a motorcycle with a new brake system.

[0006] In light of the above, it is an object of the present invention to
provide cast iron, carbon steel, stainless steel, and light weight
ceramic composite brake disks that are coated with a material that is
wear and corrosion resistant.

SUMMARY

[0007] The present invention is directed to coated brake disks, brake
drums or any mechanical device that uses friction to transfer kinetic
energy, and methods for coating brake disks in order to exhibit a three
dimensional appearance. For example, the three dimensional appearance or
surface texture can be the appearance of a woven or a textured structure
on the surface. The term brake disk is used throughout this document to
represent brake disks, brake drums or any mechanical device that uses
friction to transfer kinetic energy, for example, clutch assembly and fly
wheels. In one embodiment a brake disk has one or more surface finishes
or treatments done (generally referred to herein as surface finishing) to
the parallel working surfaces which are in turn coated with a wear and
corrosion resistant coating that exhibits a three dimensional surface
appearance or surface texture which is aesthetically pleasing. In one
embodiment at least a portion of the parallel surfaces of the brake disk
substrate is surface finished to impart a predetermined surface
irregularity, modification, design or defect that exhibit a three
dimensional appearance or surface texture. In one embodiment the surface
treatment includes a representation of a logo (for example, identifying a
manufacturer) or artistic design. The surface irregularity or defect can
be variations in the height of the parallel surfaces with angular or
perpendicular surfaces between the variations in the height of the
parallel surfaces. In addition the surface irregularity or modification
can be formed as peaks, valleys and angular surfaces between the peaks
and valleys. When the parallel surfaces of the disk brake are
subsequently coated with a coating, the disk brake can exhibit a three
dimensional appearance and/or texture. The surface finishing can be
achieved, for example, by bead blasting, sanding, grinding, acid etching,
photo-resist etching, roll forming, embossing, stamping, honing, lapping,
polishing, blanching, milling, profiling.

[0008] In one embodiment the thickness of the coating material can vary
between the peaks, valleys and angular surfaces to create the
predetermined three dimensional appearance or surface texture. For
example, more of the coating can be deposited on the peaks than is
deposited on the angular surfaces. The coating material or recipe or
construction of the coating can be selected to achieve the desired three
dimensional appearance or surface texture. Further, the coating material
can be selected to achieve different optical characteristics when applied
to the parallel surfaces of the brake disk. The brake disk can be
disk-shaped having a central hole (or in some cases multiple-holes) to
allow the brake disk to be positioned over a hub. The brake disk is
further formed with a pair of flat annular surfaces that extend from the
central hole to the periphery of the brake disk. These flat surfaces are
provided for contact with the brake pads during braking and constitute
the wear surfaces for the brake disk.

[0009] In accordance with an embodiment, the brake disk can include a cast
iron, carbon steel, light weight ceramic metallic composite, stainless
steel or a light weight ceramic composite material. A portion of the
brake disk, for example the wear or working surface, is first given a
specific surface finish and then coated with a coating material that is
wear and corrosion resistant. Further the coating material can be
deposited on portions of the brake disk that will be visible when the
brake disk is installed on the vehicle. In one embodiment, the coating is
deposited on the entire brake disk.

[0010] In one embodiment, the combination of various surface finishes with
the wear and corrosion resistant coating impart the three dimensional
appearances to the coated brake disk. The three dimensional appearance or
surface texture can be a woven or textured structure. In one embodiment
the three dimensional appearance or surface texture can be accomplished
by surface finishing at least a portion of the parallel surfaces of a
brake disk substrate to impart variations in the height of the parallel
surfaces to allow the parallel surfaces to trap particles of a coating
material. The surface finish can be introduced to the brake disk surface
by utilizing a variety of methods. These methods can be as simple as
blasting the brake disk surface with a continuous stream of particles
(commonly referred to as bead blasting) which are typically harder than
the brake disk surface. These particles can be round in shape or very
irregular in shape. The various particle shapes will impart a different
surface finish or surface geography to the brake disk. For example, with
the round particles (of various sizes) and appropriate particle energy
(air pressure or hydro pressure) a surface texture that microscopically
resembles low soft rolling hills can be achieved. With the irregular
(crystalline) shaped particles a very coarse surface geometry (very
rugged/jagged peaks and valleys) can be imparted to the brake disk
surface. Other methods such as a sanded or a ground surface finish can be
used to give a different appearance when coated with the wear and
corrosion resistant coating. When the sanded or ground surface finish is
done in a cross-hatched configuration and then coated with the wear and
corrosion resistant coating the coated brake disk can exhibit a woven
appearance or surface texture such as is found in components made from
carbon fiber. In general, there is a multitude of surface finish
techniques that can be utilized to impart a specific surface texture or
geometry into the brake disk. The techniques for the surface finishing
can include but are not limited to: bead blasting, sanding, grinding,
acid etching, laser etching, photochemical etching, roll forming,
embossing, stamping, honing, lapped, polished, blanched, milled, profiled
or other additional machined surfaces and any combination(s) thereof. The
surface finishing step can also include etching the surfaces of the brake
disk substrate. This process can be used to dissolve unwanted materials
such as metals or semiconductor materials.

[0011] In some embodiments, the coating includes a first layer of a
material having either an amorphous structure (i.e. a non-crystalline
structure) and/or a crystalline structure. In a one embodiment, the
amorphous and/or crystalline material is a metal such as titanium,
chromium, zirconium, hafnium, boron or an alloy thereof. The first layer
is applied directly on the brake disk. The coating further includes a
second layer that overlays and contacts the first layer. The second layer
can include one or more metal nitrides, metal borides, metal carbides and
metal oxides. The second layer can also include one or more nitrides,
borides, carbides or oxides of the metal used in the first layer. For
example, for a coating having titanium as the first layer, the second
layer can be titanium nitride (TiN). Note; the abbreviations (e.g. TiN)
are used herein as a shorthand rather than an exact chemical label, and
do not suggest that the stoichiometry of the indicated compound must be
exactly as stated in the abbreviation. Though the term layer is used
herein when discussing the application or depositing of materials, the
referred to layers can merge or intermingle such that no clear division
exists between the layers.

[0012] The layers of the coating can be applied using a physical vapor
deposition source such as a cathodic arc source with a controlled gas
atmosphere. Other operable techniques such as unbalanced magnetron
sputtering or thermal evaporation may also be used. During coating
deposition, the brake disks are positioned on a fixture and the fixture
is rotated in a planetary movement about a central axis. In greater
detail, the fixture includes three or more parallel poles that are
mounted on a plate and arranged wherein each pole is spaced at an equal
distance from the other poles. A plurality of brake disks can be stacked
on each pole, with spacers to separate adjacent disks within each stack.
The poles are spaced from each other to allow the brake disks on one pole
to overlap the brake disks on an adjacent pole. The spacers prevent brake
disks on one pole from contacting the brake disks on an adjacent pole.

BRIEF DESCRIPTION OF DRAWINGS

[0013] The details of the present invention, both as to its structure and
operation, may be gleaned in part by study of the accompanying drawings,
in which like reference numerals refer to like parts, and in which:

[0014] FIG. 1 is a perspective view of a motorcycle having a disk brake
system;

[0015] FIG. 2 is a perspective view of a coated disk brake;

[0016] FIG. 3A is an enlarged cross-sectional view of a portion of the
coated disk brake shown in FIG. 2 as seen along line 3-3 in FIG. 2
showing the coating layers;

[0017] FIG. 3B is an enlarged portion of FIG. 3A.

[0018] FIG. 4 is a front elevation view of a fixture for supporting the
disk brakes during the coating process;

[0019] FIG. 5 is a top plan view of a fixture for supporting the disk
brakes during the coating process;

[0020] FIG. 6 is a schematic plan view and control diagram of a deposition
apparatus for use in the invention;

[0021] FIG. 7 is a schematic perspective view of a detail of the
deposition apparatus of FIG. 5; and

[0022] FIG. 8 is a schematic cross-sectional view of a cathodic arc
source, taken along lines 8-8 of FIG. 7.

DETAILED DESCRIPTION OF THE DRAWINGS

[0023] Referring to FIG. 1, motorcycle 10 is shown that includes a disk
brake system. As shown, the disk brake system includes a brake disk 12
that is attached to the front wheel 14 of the motorcycle 10 for rotation
therewith. The brake system further includes a caliper 16 having a pair
of brake pads that can be selectively applied against the brake disk 12
using hydraulic pressure to slow the rotation of the brake disk 12 and
wheel 14. In a typical setup, the hydraulic pressure is provided by the
motorcycle operator using a hand lever mounted on the handlebars of the
motorcycle 10. A similar system can be applied to the rear wheel of the
motorcycle 10.

[0024] A better appreciation of a brake disk 12 can be obtained with
reference to FIG. 2. As shown, the brake disk 12 is disk-shaped having a
central hole 18 to allow the brake disk 12 to be positioned over the hub
of the wheel 14 (shown in FIG. 1). The brake disk 12 is further formed
with flat annular surfaces 20a,b (see also FIG. 4) that extend from the
central hole 18 to the periphery 22 of the brake disk 12. As shown, flat
surface 20a is parallel with and opposed to flat surface 20b on the brake
disk 12. These flat surfaces 20a,b are provided for contact with the
brake pads during braking and constitute the wear surfaces for the brake
disk 12. In addition, it is flat surfaces 20a,b that receive the surface
finish prior to coating with the wear and corrosion resistant coating. In
one embodiment, the brake disk is surface finished to impart a three
dimensional appearances to the brake disk before the brake disk is
coated. The three dimensional appearance or surface texture can be a
woven or textured structure. In one embodiment the three dimensional
appearance or surface texture can be accomplished by surface finishing at
least a portion of the parallel surfaces of a brake disk substrate to
impart variations in the height of the parallel surfaces to allow the
finished surfaces to receive varying amounts of the particles of a
coating material. Methods for applying the coating materials are
described below in more detail.

[0025] The surface finish can be introduced to the brake disk surface by
utilizing a variety of methods. These methods can be as simple as
blasting the brake disk surface with a continuous stream of particles
(commonly referred to as bead blasting) which are typically harder than
the brake disk surface. These particles can be round in shape or very
irregular in shape. The various particle shapes will impart a different
surface finish or surface geography to the brake disk. For example, with
the round particles (of various sizes) and appropriate particle energy
(air pressure or hydro pressure) a surface texture that microscopically
resembles low soft rolling hills can be achieved. With the irregular
(crystalline) shaped particles a very coarse surface geometry (very
rugged/jagged peaks and valleys) can be imparted to the brake disk
surface. Other methods such as a sanded or a ground surface finish can be
used to give a different appearance when coated with the wear and
corrosion resistant coating. When the sanded or ground surface finish is
done in a cross-hatched configuration and then coated with the wear and
corrosion resistant coating the coated brake disk can exhibit a woven
appearance or surface texture such as is found in components made from
carbon fiber. In general, there is a multitude of surface finish
techniques that can be utilized to impart a specific surface texture or
geometry into the brake disk. These techniques can include but are not
limited to: bead blasting, sanding, grinding, acid etching, laser
etching, photochemical etching, roll forming, embossing, stamping,
honing, lapped, polished, blanched, milled, profiled or other additional
machined surfaces and any combination(s) thereof. In one embodiment at
least a portion of the parallel surfaces of the brake disk substrate is
surface finished to impart a predetermined surface finish, irregularity,
modification or defect that exhibits a three dimensional appearance or
surface texture. The surface irregularity or defect can be variations in
the height of the parallel. In addition the surface irregularity or
modification can be formed as peaks, valleys and angular surfaces on the
parallel surfaces of the brake disk. When the parallel surfaces of the
disk brake is subsequently coated with a coating (as described below),
the disk brake exhibits a three dimensional appearance or surface
texture. The surface texture can be enhanced by controlling the
depositing of the coating, for example, by depositing more of the
material on the peaks and less of the material on the angular surfaces.
This can enhance the resulting surface texture. Additionally, the coating
can be selected such that a desired absorption or reflection of light is
achieved. In addition the composition and thickness of the coating
material to achieve a desired light reflection and absorption according
to a specific wavelength. Further, the surface texture can include a
representation of a logo or artistic design.

[0026] Referring now to FIG. 3A, a coating 24 is shown applied to a brake
disk substrate 26. For the brake disk 12, the brake disk substrate 26 can
be made of a cast iron, stainless steel or light weight ceramic composite
materials. As further shown in FIG. 3A, the coating 24 can include a
first layer 28 of a material having an amorphous structure (i.e. a
non-crystalline structure) or a crystalline structure. The first layer 28
can include multiple layers or multiple surfaces that can be merged to
form a single layer. The thickness of each layer can vary from one or a
few atoms in depth to thousands of Angstroms. The surface irregularity or
defect can be variations in the height of the parallel surfaces and
angled surfaces between the variations in height illustrated in FIG. 3B.
In addition the surface irregularity or modification can be formed as
peaks, valleys and angular surfaces between the peaks and valleys. When
the parallel surfaces of the disk brake is subsequently coated with a
coating the disk brake can exhibit a three dimensional appearance or
surface texture In addition the composition and thickness of the coating
material can be selected to achieve a desired light reflection and
absorption. In some embodiments, the amorphous or crystalline material is
a metal such as titanium, chromium, zirconium, boron, hafnium or an alloy
thereof.

[0027] Continuing with FIG. 3A, the coating 24 can also include a second
layer 30 that overlays and contacts the first layer 28. Though the layers
are depicted as distinct, in some embodiments, the layers intermingle or
merge such that no distinct boundary exists between the layers. The
second layer 30 can include one or more binary metals, for example, one
or more metal nitrides, metal borides, metal carbides and metal oxides.
The second layer can include one or more nitrides, borides, carbides or
oxides of the metal used in the first layer. In some embodiments of a
coating 24, amorphous titanium constitutes the first layer 28 and a
titanium nitride (TiN, Ti2N, etc.) constitutes the second layer 30.
The multiple layers, for example layers 28 and 30 can be configured to
form a lattice structure or a super lattice structure. These are thin
films formed by alternately depositing two different components to form
layered structures. Multilayers become superlatices when the period of
the different layers is less than 100 Å. With this cooperation of
structure, a coating 24 having a service life to exceed approximately
100,000 vehicle miles or more can be obtained. Note: the abbreviations
(e.g. TiN, Ti2N, etc.) are used herein as a shorthand rather than an
exact chemical label, and do not suggest that the stoichiometry of the
indicated compound must be exactly as stated in the abbreviation.

[0028] Referring now with cross-reference to FIGS. 4 and 5, an example
apparatus for forming the coatings will be described. A fixture 34 is
shown for holding the brake disk substrates 26 during coating. Although
the fixture 34 is shown holding five brake disk substrates 26a-e, it is
to be appreciated that the fixture 34 is merely exemplary and that fewer
or more brake disk substrates 26 could be positioned on a fixture 34. As
shown, the fixture 34 includes three parallel poles 36, 38, 40 that are
mounted on and extend from a base plate 42. Although the fixture 34 only
shows three parallel poles 36, 38, 40 it is appreciated that this
configuration is only exemplary and that fewer or more parallel poles
could be positioned on the fixture 34. The parallel poles 36, 38, 40 are
arranged on the base plate 42 with each pole 36, 38, 40 spaced at an
equal distance from the other two poles 36, 38, 40. With this cooperation
of structure, a plurality of brake disk substrates 26 can be stacked on
each pole 36, 38, 40. For example, as shown, brake disk substrates 26a
and 26d are stacked on pole 36, brake disk substrate 26c is stacked pole
38 and brake disk substrates 26b and 26e are stacked on pole 40.

[0029] Continuing with cross-reference to FIGS. 4 and 5, it can be seen
that spacers 44a-e can be used to selectively separate adjacent brake
disk substrates 26 on each pole 36, 38, 40. For the implementation shown,
each spacer 44a-e includes a tube 46 and flange 48 allowing each spacer
44a-e to be slid over a respective pole 36, 38, 40 and positioned as
desired. In the implementation shown in FIGS. 4 and 5, the spacing
between poles 36, 38 is established to allow the brake disk substrates 26
on one pole 36, 38, 40 to overlap the brake disk substrates 26 on an
adjacent pole 36, 38, 40. Also for the implementation shown in FIGS. 4
and 5, the spacers 44a-e have been sized to prevent brake disk substrates
26 on one pole 36, 38, 40 from contacting the brake disk substrates 26 on
an adjacent pole 36, 38, 40.

[0030] FIGS. 6 and 7 depict an example of a deposition apparatus 50 for
coating the brake disk substrates 26, although other operable deposition
apparatus may be used. The deposition apparatus 50 includes a chamber 52
having a body 54 and a door 56 that may be opened for access to the
interior of the chamber 52 and which is hermetically sealed to the body
54 when the chamber 52 is in operation. The interior of the chamber 52 is
controllably evacuated by a vacuum pump 58 pumping through a gate valve
60. The vacuum pump 58 includes a mechanical pump and a diffusion pump
operating together in the usual manner. The interior of the chamber 52
may be controllably backfilled to a partial pressure of a selected gas
from a gas source 62 through a backfill valve 64. The gas source 62
typically includes several separately operable gas sources. The gas
source 62 usually includes a source 62a of an inert gas such as argon and
a source 62b of Nitrogen gas, each providing gas selectively and
independently through a respective selector valve 65a or 65b. Other types
of gas can also be provided as desired, such as gases required to produce
borides, oxides and/or carbides.

[0031] The pressure within the chamber 52 is monitored by a vacuum gage
66, whose output signal is provided to a pressure controller 68. The
pressure controller 68 controls the settings of the gate valve 60 and the
backfill valve 64 (and, optionally, the selector valves 65), achieving a
balance of pumping and backfill gas flow that produces a desired pressure
in the chamber 52 and thence pressure reading in the vacuum gauge 66.
Thus, the gaseous backfilled atmosphere within the chamber 52 can be a
flowing or dynamic atmosphere.

[0032] At least two linear deposition sources 70 are mounted within the
interior of the chamber 52 in a circumferentially spaced-apart manner. In
FIG. 6, the four deposition sources are identified as distinct sources
70a, 70b, 70c, and 70d, as they will be addressed individually in the
subsequent discussion. The four deposition sources 70 are generally
rectangular bodies having a greatest rectilinear dimension elongated
parallel to a source axis 72. This type of deposition source is distinct
from either a stationary point source or a point source that moves along
the length of the substrate 26 during deposition procedures.

[0033] A support 74 is positioned in the chamber 52. The support 74
produces a compound rotational movement of a fixture 34 mounted thereon.
The support 74 can include a rotational carriage 76 that rotates about an
axis 78, driven by a rotational drive motor 80 below the rotational
carriage 76. Mounted on the rotational carriage 76 are at least one, for
example six as shown, planetary carriages 82. The planetary carriages 82
are rotationally driven about a rotational axis 84 by a planetary drive
motor 86 below the planetary carriages 82. The speeds of the rotational
drive motor 80 and the planetary drive motor 86 are controlled by a
rotation controller 88. The rotation controller 88 can rotate the
rotational carriage 76 at a rate of about 1 revolution per minute (rpm).

[0034] Continuing with FIGS. 6 and 7, for deposition processing of brake
disk substrates 26, a fixture 34 as described above can be mounted on the
planetary carriage 82, as shown. For commercial operations, a fixture 34
having a plurality of brake disk substrates 26 is typically mounted on
each planetary carriage 82 in the manner described, as illustrated for
one of the planetary carriages 82 in FIG. 6.

[0035] The temperature in the chamber 52 during deposition is controlled
using a heater 92 that extends parallel to the deposition sources 70 on
one side of the interior of the chamber 52. The heater 92 can be a
radiant heater operating with electrical resistance elements. The
temperature of the heating array is monitored by a temperature sensor 94
such as an infrared sensor that views the interior of the chamber 52. The
temperature measured by the sensor 94 is provided to a temperature
control circuit 96 that provides the power output to the heater 92.
Acting in this feedback manner, the temperature controller 96 allows the
temperature of the heating array to be set. In the processing phase, the
heating array can be heated to a temperature of from about 1000°
F. to about 1700° F.

[0036] FIG. 8 illustrates a cathodic arc source 100 that can be used in
the deposition source 70. The cathodic arc source 100 includes a
channel-shaped body 102 and a deposition target 104. The deposition
target 104 is in the form of a plate that is hermetically sealed to the
body 102 using an O-ring 106, forming a water-tight and gas-tight hollow
interior 108. The interior 108 is cooled with cooling water flowing
through a water inlet 110 and a water outlet 112. Two spirally shaped
(only sections of the spirals are seen in FIG. 8) permanent magnets 114
extend parallel to the source axis 72. Positioned above the deposition
target 104 exterior to the body 102 is a striker electrode 118. A voltage
VARC is applied between the striker electrode 118 and the deposition
target 104 by an arc source power supply 120. VARC can range from
about 10 to about 50 volts.

[0037] The metallic material that forms the deposition target 104 is
deposited onto the brake disk substrate 26 together with, if desired, gas
atoms producing gaseous species from the atmosphere of the chamber 52.
For the embodiment describe herein, the deposition target 104 is made of
Titanium (Ti) metal.

[0038] To accomplish the deposition, an arc is struck between the striker
electrode 118 and the deposition target 104, locally heating the
deposition target 104 and causing Titanium atoms and/or ions to be
ejected from the deposition target 104. (The deposition target 104 is
therefore gradually thinned as the deposition proceeds.) The striking
point of the arc on the deposition target 104 moves in a racetrack course
along the length of the deposition target 104. A negative bias voltage
VBIAS is applied between the deposition target 104 and brake disk
substrate 26 by a bias power supply 122, so that any positively charged
ions are accelerated toward the brake disk substrate 26.

[0039] VBIAS can range from about -20 to about -1000 volts. The value
selected for VBIAS determines the energy of ionic impact against the
surface of the substrates, a phenomenon termed ion peening. In a typical
case, VBIAS is initially selected to be a relatively large negative
voltage to achieve good adherence of the metallic first layer 28 (see
FIG. 3A) to the brake disk substrate 26. VBIAS is subsequently
reduced (made less negative) when the overlying hard layer is deposited,
to achieve a uniform, fine microstructure in the overlying layer. The
values of VBIAS are desirably maintained as low as possible,
consistent with obtaining an adherent coating 24. VBIAS is more
positive than -600 volts, for example -400 volts and more. If VBIAS
is too negative, corona effects and back sputtering may occur at some
regions of the brake disk substrate 26. Thus, while higher VBIAS
voltages may be used in some instances, generally VBIAS can be more
positive than -600 volts. The cathodic arc source 100 and other types of
sources, such as sputtering sources, may also be used.

[0040] The cooperative selection of the material of the deposition target
104 and the gases introduced into the deposition chamber 52 from the gas
source 62 allows a variety of coatings 24 to be deposited onto the brake
disk substrate 26, within the constraints discussed previously. The total
thickness of the coating 24 can range from about 0.5 to about 50.0
microns. If the coating thickness is less than about 1 micrometer, the
physical properties of the coating 24 are insufficient to produce the
desired results. If the coating thickness is more than about 10
micrometers, the coating 24 has a high internal stress that leads to a
tendency for the coating 24 to crack and spall away from the brake disk
substrate 26 during deposition or during service.

[0041] These general principles are applied in preparing the coatings 24
of interest, as described previously in relation to FIG. 3A. The coating
24 of FIG. 3A includes an amorphous metallic first layer 28, such as
amorphous metallic Titanium, that contacts and overlays the surface of
the brake disk substrate 26. The amorphous metallic first layer 28 is
deposited by backfilling the deposition chamber 52 with a small partial
pressure of about 5 microns of an inert gas, such as flowing argon
(flowing at a rate of about 200-450 standard cubic centimeters per minute
(sccm) in the apparatus used by the inventors), and then depositing
metal, such as Titanium, from the deposition target 104 with VBIAS
about -400 volts. Because the argon does not chemically react with the
metal, an amorphous metallic first layer 28 is deposited.

[0042] As shown in FIG. 3A, a second layer 30, which for the embodiment
described herein is a metal Nitride, overlies the amorphous metallic
first layer 28. The second layer 30 is deposited by backfilling the
deposition chamber 52 with a small partial pressure of about 5 microns of
flowing Nitrogen (flowing at a rate of about 150-500 seen in the
inventors' apparatus), and then depositing metal, such as Titanium, from
the deposition target 104 with VBIAS about -50 v

[0043] While the particular brake disks and drums, surface finishes and
methods for coating as herein shown and disclosed in detail are fully
capable of obtaining the objects and providing the advantages herein
before stated, it is to be understood that they are merely illustrative.
The described systems and methods can also be applied to other systems
such as clutch plates, clutches and flywheels. No limitations are
intended to the details of construction or design herein shown other than
as described in the appended claims.